In Eq.REF , \(\hbar {}\) , q, E, V, and \(\mathit {f}_{1,2}\)  refer to the reduced Planck constant, elementary charge of electron, energy, potential, and Fermi distribution function of leads, respectively. Near the equilibrium condition, by shedding the light on the channel, some electrons are excited to higher energy levels and their energy increases by \(\hbar {}\omega {}\)  where \(\omega {}\)  is the frequency of the incident light. After a while, they come back to lower energy levels due to losing the same energy. In consequence, we are calculating the effect of the incident light on the quantum conductance of a two levels system [1]} in which the energy of its electrons is equal to \(E\pm \hbar {}\omega {}\) . Using Fermi’s golden rule [2]}, one can calculate the electron-photon coupling matrix and consequently the self-energy of incident light to implement the influence of it on the system. This could be done by adding the mentioned self-energy to the Green’s function of the electrons similar to the effect of leads and their self energies (Appendix ). Althuogh the detailed information about incident light self-energy calculations exists in Appendix B, a brief explanation is provided in the continuation of this paragraph. In the first step, the electron and hole correlation functions and the initial value of carrier’s density are calculated by using the Green’s function of the channel and self-energies of leads without shedding the light (zero self-energy of the photon). By means of the coupling matrix and correlation functions, one can calculate the initial value of photon self-energy which is used for evaluating the new amount of the Green’s function of the channel and the self-energy of the photon. Using Poisson’s equation, the loop is repeated until the convergence is achieved i.e., it is a self-consistent method (Appendix ) in accordance with Fig.REF .
